Stimulation of beta-adrenergic receptors (B-AR) on the tracheobronchial epithelium elicits a variety of cellular responses which affect the defense of the respiratory tract and which may alter the intensity of the inflammatory response in the airway. The objectives of this proposal are to characterize the B-AR coupled adenyly cyclase system in isolated tracheobronchial epithelial cells obtained from rabbits and humans. These studies should help elucidate the mechanisms regulating the B-AR-coupled adenylyl cyclase system.